Crisis in Ukraine: What you need to know

The United States escalated its response to Russia’s military and economic threats to Ukraine on Thursday, announcing it has imposed visa bans on officials and others deemed responsible for actions that have undermined Ukraine’s sovereignty and territorial integrity. The announcement came as the European Union was considering its own punitive measures and as Secretary of State John Kerry met for a second day with the Russian foreign minister, Sergey V. Lavrov, on ways to defuse the Ukraine crisis, one of the most serious East-West confrontations since the Cold War.